Synthesis and In Situ Behavior of 1,4- and 2,5-(13C) Isotopomers of p-Phenylenediamine in Reconstructed Human Epidermis Using High Resolution Magic Angle Spinning NMR.

p-Phenylenediamine (PPD) has been classified as a strong skin allergen, but when it comes to toxicological concerns, benzoquinone diamine (BQDI), the primary oxidation derivative of PPD, is frequently considered and was shown to covalently bind nucleophilic residues on model peptides. However, tests in solution are far from providing a reliable model, as the cutaneous metabolism of PPD is not covered. We now report the synthesis of two 13C substituted isotopomers of PPD, 1,4-(13C)p-phenylenediamine 1 and 2,5-(13C)p-phenylenediamine 2, and the investigation of their reactivity in reconstructed human epidermis (RHE) using the high resolution magic angle spinning (HRMAS) NMR technique. RHE samples were first treated with 1 or 2 and incubated for 1 to 48 h. Compared to the control, spectra clearly showed only the signals of 1 or 2 gradually decreasing with time to disappear after 48 h of incubation. However, the culture media of RHE incubated with 1 for 1 and 24 h, respectively, showed the presence of both monoacetylated- and diacetylated-PPD as major products. Therefore, the acetylation reaction catalyzed by N-acetyltransferase (NAT) enzymes appeared to be the main process taking place in RHE. With the aim of increasing the reactivity by oxidation, 1 and 2 were treated with 0.5 equiv of H2O2 prior to their application to RHE and incubated for different times. Under these conditions, new peaks having close chemical shifts to those of PPD-cysteine adducts previously observed in solution were detected. Under such oxidative conditions, we were thus able to detect and quantify cysteine adducts in RHE (maximum of 0.2 nmol/mg of RHE at 8 h of incubation) while no reaction with other nucleophilic amino acid residues could be observed.

In Situ Alkylation of Reconstructed Human Epidermis by Methyl Methanesulfonate: A Quantitative HRMAS NMR Chemical Reactivity Mapping.

Allergic contact dermatitis (ACD) is a reaction of the immune system resulting from skin sensitization to an exogenous hazardous chemical and leading to the activation of antigen-specific T-lymphocytes. The adverse outcome pathway (AOP) for skin sensitization identified four key events (KEs) associated with the mechanisms of this pathology, the first one being the ability of skin chemical sensitizers to modify epidermal proteins to form antigenic structures that will further trigger the immune system. So far, these interactions have been studied in solution using model nucleophiles such as amino acids or peptides. As a part of our efforts to better understand chemistry taking place during the sensitization process, we have developed a method based on the use of high-resolution magic angle spinning (HRMAS) NMR to monitor in situ the reactions of 13C substituted chemical sensitizers with nucleophilic amino acids of epidermal proteins in reconstructed human epidermis. A quantitative approach, developed so far for liquid NMR applications, has not been developed to our knowledge in a context of a semisolid nonanisotropic environment like the epidermis. We now report a quantitative chemical reactivity mapping of methyl methanesulfonate (MMS), a sensitizing methylating agent, in reconstructed human epidermis by quantitative HRMAS (qHRMAS) NMR. First, the haptenation process appeared to be much faster in RHE than in solution with a maximum concentration of adducts reached between 4 and 8 h. Second, it was observed that the concentration of cysteine adducts did not significantly increase with the dose (2.07 nmol/mg at 0.4 M and 2.14 nmol/mg at 1 M) nor with the incubation time (maximum of 2.27 nmol/mg at 4 h) compared to other nucleophiles, indicating a fast reaction and a potential saturation of targets. Third, when increasing the exposure dose, we observed an increase of adducts up to 12.5 nmol/mg of RHE, excluding cysteine adducts, for 3112 µg/cm2 (1 M solution) of (13C)MMS. This methodology applied to other skin sensitizers could allow for better understanding of the potential links between the amount of chemical modifications formed in the epidermis in relation to exposure and the sensitization potency.

Effect of deep transverse friction massage vs stretching on football players' performance.

BACKGROUND: Flexibility, agility and muscle strength are key factors to either win or lose a game. Recently the effect of a new technique, deep transverse friction massage (DTFM) on muscle extensibility as compared to traditional stretching techniques has been examined. AIM: To compare the effect of DTFM vs static and dynamic stretching techniques on the hamstring's extensibility, agility, and strength amongst Lebanese and Syrian football players. Recording the incidence of non-contact hamstring muscle injury was a secondary objective. METHODS: This study is a single-blinded prospective longitudinal randomized controlled trial. The experiment took place over a period of four weeks. Football players were randomized into three intervention groups (static stretching; dynamic stretching; DTFM). Participants of each group were followed-up carefully by assessors during their intervention sessions three times per week, for a total of 12 sessions and during the data collection. Extensibility, agility, and strength were compared between intervention groups at (baseline; acute; and chronic) phases. Straight leg raise and 1 repetition maximum tests were used to measure the dominant leg hamstring muscle extensibility and maximal strength respectively. T-drill test was used to assess the lower extremities agility. RESULTS: Of 103 Lebanese and Syrian male football players aged between 18 and 35 were sampled from Damascus-Syria and South of Lebanon to participate in this study. Between-groups measures of acute strength (P = 0.011) and chronic extensibility (P = 0.000) solely showed a significant difference, and the static group showed to be superior as compared to the other groups. No loss to follow-up or protocol violation was recorded. CONCLUSION: Static stretching is showing to be superior to the other techniques used, regarding gaining long-term extensibility and short-term maximal muscle strength. In addition, DTFM showed improvements but did not outweigh the effects on footballers' performance when comparing it to static and dynamic techniques. Finally, no difference between the interventions is recorded regarding the rate of muscle injuries incidence.

Ion pairing controls rheological properties of "processionary" polyelectrolyte hydrogels.

We demonstrated recently that polyelectrolytes with cationic moieties along the chain and a single anionic head are able to form physical hydrogels due to the reversible nature of the head-to-body ionic bond. Here we generate a variety of such polyelectrolytes with various cationic moieties and counterion combinations starting from a common polymeric platform. We show that the rheological properties (shear modulus, critical strain) of the final hydrogels can be modulated over three orders of magnitude depending on the cation/anion pair. Our data fit remarkably well within a scaling model involving a supramolecular head-to-tail single file between cross-links, akin to the behaviour of pine-processionary caterpillar. This model allows the quantitative measure of the amount of counterion condensation from standard rheology procedure.

Mediating gel formation from structurally controlled poly(electrolytes) through multiple "head-to-body" electrostatic interactions.

Tuning the chain-end functionality of a short-chain cationic homopolymer, owing to the nature of the initiator used in the atom transfer radical polymerization (ATRP) polymerization step, can be used to mediate the formation of a gel of this poly(electrolyte) in water. While a neutral end group gives a solution of low viscosity, a highly homogeneous gel is obtained with a phosphonate anionic moiety, as characterized by rheometry and diffusion nuclear magnetic resonance (NMR). This novel type of supramolecular control over poly(electrolytic) gel formation could find potential use in a variety of applications in the field of electro-active materials.

Enantioselective manganese-porphyrin-catalyzed epoxidation and C-H hydroxylation with hydrogen peroxide in water/methanol solutions.

The asymmetric epoxidation of alkene and hydroxylation of arylalkane derivatives by H(2)O(2) to give optically active epoxides (enantiomeric excess (ee) up to 68%) and alcohols (ee up to 57%), respectively, were carried out in water/methanol solutions using chiral water-soluble manganese porphyrins as catalysts.